internal constructor and delegates for testing

src/OpenTelemetry.ResourceDetectors.Host/HostDetector.cs

@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
+using System.Runtime.CompilerServices;
 using System.Text;
 using Microsoft.Win32;
 using OpenTelemetry.Resources;
@@ -16,6 +17,34 @@ namespace OpenTelemetry.ResourceDetectors.Host;
 /// </summary>
 public sealed class HostDetector : IResourceDetector
 {
+    private readonly PlatformID platformId;
+    private readonly Func<string> getMacOsMachineId;
+    private readonly Func<string> getWindowsMachineId;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="HostDetector"/> class.
+    /// </summary>
+    public HostDetector()
+        : this(
+        Environment.OSVersion.Platform,
+        GetMachineIdMacOs,
+        GetMachineIdWindows)
+    {
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="HostDetector"/> class for testing.
+    /// </summary>
+    /// <param name="platformId">Target platform ID.</param>
+    /// <param name="getMacOsMachineId">Function to get MacOS machine ID.</param>
+    /// <param name="getWindowsMachineId">Function to get Windows machine ID.</param>
+    internal HostDetector(PlatformID platformId, Func<string> getMacOsMachineId, Func<string> getWindowsMachineId)
+    {
+        this.platformId = platformId;
+        this.getMacOsMachineId = getMacOsMachineId ?? throw new ArgumentNullException(nameof(getMacOsMachineId));
+        this.getWindowsMachineId = getWindowsMachineId ?? throw new ArgumentNullException(nameof(getWindowsMachineId));
+    }
+
     /// <summary>
     /// Detects the resource attributes from host.
     /// </summary>
@@ -27,7 +56,7 @@ public Resource Detect()
             return new Resource(new List<KeyValuePair<string, object>>(1)
             {
                 new(HostSemanticConventions.AttributeHostName, Environment.MachineName),
-                new(HostSemanticConventions.AttributeHostId, GetMachineId()),
+                new(HostSemanticConventions.AttributeHostId, this.GetMachineId()),
             });
         }
         catch (InvalidOperationException ex)
@@ -39,39 +68,6 @@ public Resource Detect()
         return Resource.Empty;
     }
 
-    private static string GetMachineId()
-    {
-        return Environment.OSVersion.Platform switch
-        {
-            PlatformID.Unix => GetMachineIdLinux(),
-            PlatformID.MacOSX => GetMachineIdMacOs(),
-            PlatformID.Win32NT => GetMachineIdWindows(),
-            _ => string.Empty,
-        };
-    }
-
-    private static string GetMachineIdLinux()
-    {
-        var paths = new[] { "/etc/machine-id", "/var/lib/dbus/machine-id" };
-
-        foreach (var path in paths)
-        {
-            if (File.Exists(path))
-            {
-                try
-                {
-                    return File.ReadAllText(path).Trim();
-                }
-                catch (Exception ex)
-                {
-                    HostResourceEventSource.Log.ResourceAttributesExtractException(nameof(HostDetector), ex);
-                }
-            }
-        }
-
-        return string.Empty;
-    }
-
     private static string GetMachineIdMacOs()
     {
         var startInfo = new ProcessStartInfo
@@ -98,4 +94,37 @@ private static string GetMachineIdWindows()
         return Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\Cryptography", false)?.GetValue("MachineGuid") as string ?? string.Empty;
     }
 #pragma warning restore CA1416
+
+    private string GetMachineId()
+    {
+        return this.platformId switch
+        {
+            PlatformID.Unix => this.GetMachineIdLinux(),
+            PlatformID.MacOSX => this.getMacOsMachineId(),
+            PlatformID.Win32NT => this.getWindowsMachineId(),
+            _ => string.Empty,
+        };
+    }
+
+    private string GetMachineIdLinux()
+    {
+        var paths = new[] { "/etc/machine-id", "/var/lib/dbus/machine-id" };
+
+        foreach (var path in paths)
+        {
+            if (File.Exists(path))
+            {
+                try
+                {
+                    return File.ReadAllText(path).Trim();
+                }
+                catch (Exception ex)
+                {
+                    HostResourceEventSource.Log.ResourceAttributesExtractException(nameof(HostDetector), ex);
+                }
+            }
+        }
+
+        return string.Empty;
+    }
 }

test/OpenTelemetry.ResourceDetectors.Host.Tests/HostDetectorTests.cs

@@ -1,7 +1,10 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
+using System;
+using System.IO;
 using System.Linq;
+using System.Text;
 using OpenTelemetry.Resources;
 using Xunit;
 
@@ -21,4 +24,42 @@ public void TestHostAttributes()
         Assert.NotEmpty(resourceAttributes[HostSemanticConventions.AttributeHostName]);
         Assert.NotEmpty(resourceAttributes[HostSemanticConventions.AttributeHostId]);
     }
+
+    [Fact]
+    public void TestHostMachineId()
+    {
+        var etcMachineIdStream = (string path) =>
+        {
+            return path == "/etc/machine-id"
+                ? new MemoryStream(Encoding.UTF8.GetBytes("etc-machine-id"))
+                : null;
+        };
+        var varLibDbusMachineIdStream = new MemoryStream(Encoding.UTF8.GetBytes("var-lib-dbus-machine-id"));
+    }
+
+    [Fact]
+    public void TestHostMachineIdMacOs()
+    {
+        var detector = new HostDetector(
+            PlatformID.MacOSX,
+            () => "macos-machine-id",
+            () => throw new Exception("should not be called"));
+        var resource = ResourceBuilder.CreateEmpty().AddDetector(detector).Build();
+        var resourceAttributes = resource.Attributes.ToDictionary(x => x.Key, x => (string)x.Value);
+        Assert.NotEmpty(resourceAttributes[HostSemanticConventions.AttributeHostId]);
+        Assert.Equal("macos-machine-id", resourceAttributes[HostSemanticConventions.AttributeHostId]);
+    }
+
+    [Fact]
+    public void TestHostMachineIdWindows()
+    {
+        var detector = new HostDetector(
+            PlatformID.Win32NT,
+            () => throw new Exception("should not be called"),
+            () => "windows-machine-id");
+        var resource = ResourceBuilder.CreateEmpty().AddDetector(detector).Build();
+        var resourceAttributes = resource.Attributes.ToDictionary(x => x.Key, x => (string)x.Value);
+        Assert.NotEmpty(resourceAttributes[HostSemanticConventions.AttributeHostId]);
+        Assert.Equal("windows-machine-id", resourceAttributes[HostSemanticConventions.AttributeHostId]);
+    }
 }